Electrochemical studies of the reduction and oxidation of t-BuC60- have been conducted at platinum electrodes in tetrahydrofuran and dimethyl sulfoxide. The formal potentials for the first three steps of reduction are reported and compared to those of C-60. The fact that these potentials are displaced in the negative direction from those of C-60 has been interpreted in terms of the dominance of electrostatic effects in determining the potentials of fullerenes and their derivatives. Oxidation of t-BuC60- gives the corresponding radical which takes part in a reversible dimerization reaction. The cyclic voltammetric behavior as a function of scan rate and concentration is consistent with this mechanism and simulations of the data have provided limits on the dimerization equilibrium and rate constants. Specifically, the equilibrium constant falls in the range of 1.9 to 14 x 10(7) M-1 and the rate constant for dimerization is 2 to 40 x 10(8) M-1 s(-1).